1. Field of the Invention
The present invention relates to steam irons for flattening wrinkles, etc., of clothes by providing moisture.
2. Description of the Prior Art
Steam irons are used with tap water in general. However, since tap water contains inorganic substances such as calcium and sodium, they remain within a steam iron as evaporation residue after the water is evaporated inside a vaporization chamber if untreated tap water is used, and they gradually accumulate as the scale within the vaporization chamber and a steam passageway from the vaporization chamber to a steam nozzle. If the iron is used for a long time, narrow portions of the steam passageway are eventually clogged and spray of steam is obstructed. Some countermeasures are devised in order to avoid adverse effects this kind due to the scale.
A first example is a means to use an ion exchange resin in order to reduce deposit of the scale by turning water into soft water or demineralized water, as disclosed in the Japanese Patent Examined Publication No. S59-35640.
A second example is to place an inhibitor, a chelating agent, etc. in a water tank and dissolve them into water inside the water tank so as to discharge the scale outside of the steam iron with a flow of steam, as the scale decreases its mechanical strength and becomes less liable to adhere due to an effect of the inhibitor or the chelating agent dissolved in the water, as disclosed in the Japanese Patent Laid-Open Publication No. S61-179194.
A third example is to dissolve phosphonate compound into water in the water tank so as to reduce deposit of the scale by an effect of the phosphonate compound dissolved in the water, as disclosed in the Japanese Patent Laid-Open Publication No. H06-254299.
However, the first example is not suitable for ordinary households because it is difficult to manage for maintaining the water quality properly as a time period in which the ion exchange resin can keep the original efficiency is short.
Also, the second and the third examples have a problem in that particles of the scale which are discharged outside of the iron with the steam are so large that they tend to stick to clothes being ironed and are conspicuous.